Semiconductor devices including a compound such as GaN or AlGaN are utilized in various applications to semiconductor devices such as light emitting devices or light receiving devices since they have many advantages, for example, of wide and easily adjustable bandgap energy or the like.
Light emitting devices include light emitting diodes using a Group III-V or II-VI compound semiconductor material, laser diodes, or the like. By virtue of the developments of thin film growth technique and element material, a light emitting device may implement not only a variety of colors of light such as red, green, blue and UV light, but also white light with excellent efficacy by using a fluorescent material or combining colors, and has advantages of low power consumption, semi-permanent lifespan, rapid response speed, safety and environmental friendliness, as compared to conventional light sources such as fluorescent lamps and incandescent lamps. Accordingly, the application range of the light emitting device has expanded to a transmission module of optical communication equipment, a light emitting diode backlight that replaces a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD) device, a white light emitting diode illuminating apparatus that replaces a fluorescent or incandescent lamp, a headlight for vehicles, and a signal light.
A photodetector, which is an example of the light receiving device, is a kind of transducer that detects light and converts the intensity of the light into an electric signal. A light receiving device using a semiconductor converts electromagnetic energy into electric energy based on the photoelectric effect generated in a semiconductor. Such a light receiving device may be implemented in a variety of forms. Among light receiving devices with various structures, PIN diode-type structures have excellent response characteristics and research to improve responsivity of light receiving devices using the same is thus underway.
Carriers may be multiplied by increasing an electric field in a depletion region through application of a high reverse bias voltage to a PIN diode-type light receiving device. As such, response characteristics of light receiving devices which utilize a PIN diode-type structure are related to the area (or size) of the depletion region. Conventional light receiving devices have a drawback of poor response characteristics due to narrow depletion regions. In addition, PIN-type light receiving devices may have a problem of requiring application of a negative bias so as to have the region I completely depleted.